The present invention relates to astronomical telescopes, and more particularly to a system and method for enabling the viewing of distant astronomical objects with greater resolution and/or light gathering power than that which can presently be achieved with ground-based telescopes.
Since the days of the great Italian scientist and astronomer Galileo, the resolution and light gathering power of astronomical telescopes has been continually improved. It is difficult to make lenses of the type utilized in ground-based telescopes where a lens diameter of more than about 40 inches is required. Therefore, where a telescope with great light gathering power has been desired a concave mirror instead of a lens has been used as the objective element. An example of one such reflecting telescope is located at Mt. Palomar in the State of California, in the United States of America. That telescope has a concave mirror with a diameter of approximately 200 inches.
It is difficult to increase the light gathering power of a single large mirror reflecting telescope beyond that which has already been achieved due to practical restraints. This is because a very large reflecting mirror tends to sag under its own weight when the telescope is pivoted, thus distorting its reflecting surface and imparing resolution.
Multiple mirror telescopes have been constructed in which a plurality of large reflecting mirrors are mounted symmetrically about a central axis in order to focus light into a common image. An example of a telescope of this design is located at Mt. Hopkins, in the State of Arizona, in the United States of America. That telescope utilizes six 72 inch concave reflecting mirrors. This approach could be used to achieve greater light gathering power and/or resolution than single reflecting mirror telescopes. However, it is probably not practical to use the multiple mirror approach to achieve an improvement of more than about one order of magnitude in either of these factors.
Where a telescope has been designed to maximize light gathering power it has often resulted in a telescope having lower quality resolution than telescopes having significantly less light gathering power. For example, the refracting telescope located at Lowell Observatory in the State of Arizona, in the United States utilizes a 24 inch lens yet it has better resolution than the reflecting telescope located at Mt. Palomar.
When making astronomical observations from the surface of the earth, a number of factors limit the resolution which can be achieved with conventional telescopes. Scintillation due to lack of homogenity of the vapor content of the earth's atmosphere represents a principal limitation on resolution which can be achieved. Back scattered light also impairs viewing capability. The effects of light from the sun and the moon can be minimized by making astronomical observations at the appropriate time. However, artificial man-made lighting emanating from the surface of the earth is increasingly becoming a problem. Finally, air pollution also impairs the resolution which can be achieved with ground-based astronomical telescopes.
In an effort to minimize the degrading effects of scintillation, back scattered light and air pollution, large astronomical telescopes are typically mounted on remote mountain tops. Astronomical telescopes have also been flown in jet aircraft to high altitudes, for example 45,000 feet. Recently, a complete reflecting telescope has been placed into orbit about the earth and pictures have been transmitted by RF signals to ground receiving stations. While such airborne and orbiting telescopes have resulted in greater resolution, clearly the light gathering power of such telescopes is limited. Heretofore, astronomical telescopes with very great light gathering power have been very large and heavy, making it impractical to carry them to high altitudes in aircraft or to place them into orbit about the earth.
In the May, 1980 issue of the magazine entitled "ASTRONAUTICS AND AERONAUTICS" there is briefly described on pages 65 and 66 a proposed radio telescope system employing a large orbiting Fresnel zone plate as the objective lens and a plurality of spaced apart, orbiting sensing satellites positioned at different foci of the zone plate. Another telescope system in which adjacent orbiting satellites would carry the objective lens and sensing units, respectively, is believed to have been proposed by the Jet Propulsion Laboratory (JPL), in Pasadena in the State of California, in the United States. However, details of the JPL system are not available.